Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$36.98	12.255%	$41.5119	$41.51	$41.50	$41.50
Purchase #2	$222.78	11.493%	$248.3841	$248.38	$248.40	$248.40
Purchase #3	$151.57	9.315%	$165.6887	$165.69	$165.70	$165.70
Purchase #4	$165.46	6.861%	$176.8122	$176.81	$176.80	$176.80
Purchase #5	$126.90	9.550%	$139.019	$139.02	$139.00	$139.00
Purchase #6	$58.61	4.549%	$61.2762	$61.28	$61.30	$61.30
Purchase #7	$233.76	3.285%	$241.439	$241.44	$241.45	$241.40
7 purchase totals =	$996.06		$1,074.1311	$1,074.13	$1,074.15	$1,074.10